Relic neutrino freeze-out: Dependence on natural constants

2014/06/30 by Jeremiah Birrell, Cheng Tao Yang, Cheng-Tao Yang +1
Mathematics · Physics and Astronomy · #Astrophysics #Boltzmann constant #Boltzmann equation #Computation #Cosmic microwave background #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Lepton #Mathematics #Neutrino #Neutrino Physics Research #Nuclear physics #Particle physics #Physics #Quantum mechanics #Solver #Statistical physics #Universe #Weinberg angle #astro-ph.CO #hep-ph #nucl-th

paper · pdf · doi:10.1016/j.nuclphysb.2014.11.020

published as Nucl. Phys. B 890, 481 (2015) · 38 pages, 14 figures

openalex publication_date 2014/11/29 · arxiv created 2014/12/12 · arxiv updated 2015/06/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Analysis of cosmic microwave background radiation fluctuations favors an effective number of neutrinos, Nν>3. This motivates a reinvestigation of the neutrino freeze-out process. Here we characterize the dependence of Nν on the Standard Model (SM) parameters that govern neutrino freeze-out. We show that Nν depends on a combination η of several natural constants characterizing the relative strength of weak interaction processes in the early Universe and on the Weinberg angle sin2⁡θW. We determine numerically the dependence Nν(η,sin2⁡θW) and discuss these results. The extensive numerical computations are made possible by two novel numerical procedures: a spectral method Boltzmann equation solver adapted to allow for strong reheating and emergent chemical non-equilibrium, and a method to evaluate Boltzmann equation collision integrals that generates a smooth integrand.

Citations

• Baryon Number Violation
• General Relativity and the Einstein Equations
• Grand Unification and Time Variation of the Gauge Couplings
• Relic neutrino decoupling including flavour oscillations
• Big Bang Nucleosynthesis Predictions for Precision Cosmology
• The Einstein-Vlasov System/Kinetic Theory
• Review of particle properties
• Big Bang Nucleosynthesis: Theories and Observations
• Varying constants, Gravitation and Cosmology
• The Primordial Lithium Problem
• Planck2013 results. XVI. Cosmological parameters
• A Spectral Transform Method for Singular Sturm-Liouville Problems with Applications to Energy Diffusion in Plasma Physics
• Light Sterile Neutrinos: A White Paper

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